diffusers are meant to be open to the ground not closed off like this. obviously it would be difficult for a road car but they also should be as close to the ground as possible and the roof should sit at around 9 degrees.
I spoke to this guy today. The pic is a first prototype meant for road cars. The race car version is due for completion next week and will be considerably different. The exhaust exits through the box. HAve a look at the web site. His front bar extension mods are really NICE.
on older road cars additions like splitters and rear diffusers contribute as much to downforce (or in reality reduction of lift) through cleaning up the airflow as they do through actually working the air. so these rear diffusers we're looking at will clean up the flow out the back of the car by straightening it, and stopping the air hitting the inside of the rear bar. the effect is not as great on 2+2 cause of the fuel tank but it's not a smooth surface through there anyway. agree the design of these diffusers are not particuarly aggressive, but at the sort of ride heights ppl are likely to want on their trackable street cars you're not going to actually get much real downforce anyway. drag reduction however is a different matter.
He is going to send some poics of the track version when they are finshed in a week or so. http://simtecmotorsports.com/index.htm
